package com.uchiha.nova.core.service;

import java.io.*;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

/**
 * @author 周林静
 * @Date 2021-10-26 9:36
 * @Version 1.0
 */
class ServicesFiles {
    private static final Charset UTF_8 = StandardCharsets.UTF_8;

    /**
     * Reads the set of service classes from a service file.
     *
     * @param input not {@code null}. Closed after use.
     * @return a not {@code null Set} of service class names.
     * @throws IOException
     */
    static Set<String> readServiceFile(InputStream input) throws IOException {
        HashSet<String> serviceClasses = new HashSet<>();
        try (
                InputStreamReader isr = new InputStreamReader(input, UTF_8);
                BufferedReader r = new BufferedReader(isr)
        ) {
            String line;
            while ((line = r.readLine()) != null) {
                int commentStart = line.indexOf('#');
                if (commentStart >= 0) {
                    line = line.substring(0, commentStart);
                }
                line = line.trim();
                if (!line.isEmpty()) {
                    serviceClasses.add(line);
                }
            }
            return serviceClasses;
        }
    }

    /**
     * Writes the set of service class names to a service file.
     *
     * @param output   not {@code null}. Not closed after use.
     * @param services a not {@code null Collection} of service class names.
     * @throws IOException
     */
    static void writeServiceFile(Collection<String> services, OutputStream output) throws IOException {
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(output, UTF_8));
        for (String service : services) {
            writer.write(service);
            writer.newLine();
        }
        writer.flush();
    }
}
